/*
  将下面异步代码使用 Promise 的方法改进
  尽量用看上去像同步代码的方式
  setTimeout(function () {
    var a = 'hello'
    setTimeout(function () {
      var b = 'lagou'
      setTimeout(function () {
        var c = 'I ♥ U'
        console.log(a + b +c)
      }, 10)
    }, 10)
  }, 10)
*/

function proString(val){
    return new Promise(function (resolve,reject){
        setTimeout(function(){
            resolve(val)
        },10)
    })
}

const promise = proString('')
promise.then((val)=>{
    val+='hello'
    return val
}).then((val)=>{
    val+='lagou'
    return val
}).then((val)=>{
    val+='I love u'
    console.log(val)
    return val
})

